Using x-ray spectroscopy, we demonstrate the existence of 0.3-6 keV electrons in a low-pressure, low-power, magnetized plasma source, heated by an external radio-frequency antenna located at one end of an axisymmetric tandem mirror. X-ray measurements on low-bulk-temperature, Te,b ∼ 4 eV, hydrogen, neon, argon, and gas-mixture plasmas show spectra with high-energy tails having a near-Maxwellian form with Te,f up to 650 eV. The fast electrons producing these x-rays have densities in the range of 107-109 cm-3, 0.01%-1% of the bulk plasma density (up to 3 × 1011 cm-3), and so carry a significant fraction of the plasma energy and represent an important mechanism relevant to power coupling and heat flow in similar plasma sources.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics